• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.199.2-199.2
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• 2015

전이금속 칼코겐화합물(TMD)은 2차원 박막 물질로, 그래핀과 함께 차세대 사물인터넷에 적용할 수 있는 전자소자의 소재로 활용될 것으로 기대되고 있다. 특히 TMD는 그래핀과 다르게 1.2 eV 이상의 넓은 밴드갭을 지녀, 기존 실리콘 기반 반도체 소자를 대체할 차세대 물질로 각광받고 있다. TMD는 또한 실리콘 등의 3차원 반도체보다 광전효율이 뛰어나며, 이를 활용한 광전소자의 개발 및 연구가 활발히 진행되고 있다. 그러나 TMD는 그 두께가 나노미터 단위로 매우 얇아 광흡수율이 매우 떨어지는 단점이 있다. 우리는 이러한 TMD 기반 광전소자의 광흡수율을 향상시키기 위해 광전효율이 매우 뛰어난 페로브스카이트(Perovskite)를 TMD 채널 위에 덮음으로써, 이종접합 광전소자를 구현하였다. TMD 물질은 이황화 몰리브데넘($MoS_2$)을 선택하였으며, 광흡수층으로 선택한 페로브스카이트는 $MAPbI_3$을 스핀 코팅을 통해 TMD 채널 층에 접합하였다. 우리는 Photoluminescence 및 UV-Vis 측정을 통해 페로브스카이트 및 페로브스카이트/$MoS_2$ 층의 광특성을 측정하여 페로브스카이트에서 생성된 광캐리어가 확산되어 $MoS_2$에 전달되는 것을 확인하였다. 우리는 추가로 4가지 서로 다른 파장대의 레이저(520, 655, 785, 850 nm)를 이용하여 페로브스카이트 광흡수층이 있을 때와 없을 때의 $MoS_2$ 광검출기의 성능 변화를 관찰하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.70.2-70.2
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• 2015

현재 반도체 및 디스플레이이 공정 분야는 1 um 이상의 입자에서부터 10 nm이하 크기의 오염입자를 제어해야 한다. 현재 오염원인을 파악하기 위해서 사용하는 방법은 공정 완료 후 대상물(웨이퍼 및 글래스)을 CD-SEM (Critical Dimension Scanning Electron Microscope)와 같은 첨단 분석장비를 사용하여 사후 (Ex-situ) 진행하고 있다. 이러한 방법은 오염원이 이미 공정 대상물을 오염시키고 난 후 그 원인을 분석하는 방법으로 그 원인을 찾기가 어려울 뿐만 아니라, 최근 공정관리가 공정 진행 중(In-situ) 행해져야 하는 추세로 봤을 때 합당한 방법이라 할 수 없다. 이를 해결하기 위해 진공공정 중 레이저를 이용하여 측정하고자 하는 여러 시도들이 있었지만, 여전히 긍정적인 답변을 보여주지 못하고 있다. 본 발표에서 소개하는 PCDS (Particle Characteristic Diagonosis System)은 PBMS (Particle Beam Mass Spectrometer)와 SEM (Scanning Electron Microscope), 그리고 EDS (Energy Dispersive X-ray Spectroscopy)를 통합하여 만든 시스템으로 진공공정 중 (In-situ) 챔버 내부에서 발생하고 있는 입자의 크기 분포, 입자의 형상, 그리고 입자의 성분을 실시간으로 분석할 수 있는 방법을 제공한다. 이러한 방법 (PCDS)에 대한 개념과 원리, 그리고 현재까지 개발된 단계에서 얻어진 결과에 대해 소개할 것이다.

• Korean Journal of Optics and Photonics
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• v.14 no.4
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• pp.454-459
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• 2003

We report the first demonstration of 10 Gb/s wavelength conversion in a Mach-Zehnder interferometric wavelength converter monolithically integrated with a loss-coupled DFB probe source. The integrated device is fabricated using a BRS (buried ridge stripe) structure with an undoped InP clad layer on the top of a passive waveguide to reduce high propagation loss. The device exhibited a static extinction ratio of 11 dB. Good performance at 10 Gb/s is obtained with an extinction ratio of 7 dB and a power penalty of 2.8 dB at a 10$^{-9}$ bit error rate.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.316-316
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• 2013

실리콘(Si)은 이미지 센서, 포토검출기, 태양전지등 반도체 광전소자 분야에서 널리 사용되고 있는 대표적인 물질이다. 이러한 소자들은 광추출 또는 광흡수 효율을 향상시키는 것이 매우 중요하다. 그러나 Si의 높은 굴절율은 표면에서 30% 이상의 반사율을 발생시켜 소자의 성능을 저하시킨다. 따라서, 표면에서의 광학적 손실을 줄이기 위한 효과적인 무반사 코팅이 필요하다. 최근, 우수한 내구성과 광대역 파장 및 다방향성에서 무반사 특성을 보이는 서브파장 주기를 갖는 나노격자(subwavelength grating, SWG) 구조의 형성 및 제작에 관한 연구가 활발히 진행되고 있다. 이러한 구조는 경사 굴절율 분포를 가지는 유효 매질을 형성시킴으로써 Fresnel 반사율을 감소시킬 수 있어 반도체 소자 표면에서의 광손실을 줄일 수 있다. 그러나, SWG나노구조는 식각에 의한 표면 결함(defects)들이 발생하게 된다. 이러한 결함은 표면에서의 재결합 손실을 발생시켜 소자의 성능을 크게 저하시킨다. 이러한 문제를 해결하기 위해, 표면 보호막 및 무반사 코팅 층을 목적으로 하는 산화막을 표면에 형성시키기도 한다. 따라서 본 실험에서는 레이저간섭리소그라피 및 건식 식각을 이용하여 Si 기판에 SWG 나노구조를 형성하였고, 제작된 샘플 표면 위에 실리콘 산화막(SiOx)을 furnace를 이용하여 형성시켰다. 제작된 샘플들의 표면 및 식각 profile은 scanning electron microscope를 사용하여 관찰하였으며, UV-vis-NIR spectrophotometer 를 사용하여 빛의 입사각에 따른 반사율을 측정하였고, 표면 접촉각 측정 장비를 이용하여 표면 wettability를 조사하였다.

• Journal of the Semiconductor & Display Technology
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• v.12 no.1
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• pp.15-21
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• 2013

In this paper, sensor system and inspection algorithm in order to inspect steel balance weight for automobile is described. Steel balance weight is composed of clip and weight, which is joined by press process. The defective one has a gap between clip and weight. To detect whether there is a gap, sensor system is simply configured with laser line projector and USB camera, which make it possible to measure the height difference of clip and weight area. Laser line pattern which is made on the surface of a balance weight is captured by USB camera. In case that USB camera is used in machine vision, barrel distortion caused by wide angle lens makes the captured image distorted. Image warping function is applied to correct the distortion. Simple image processing algorithm is applied to extract the laser line information and whether it is good or not is judged through the extracted information.

• Journal of the Semiconductor & Display Technology
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• v.5 no.3 s.16
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• pp.5-10
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• 2006

This paper investigates cutting qualities after laser dicing and predicts the problems that can be generated by laser dicing. And through 3 point bending test, die strength is measured and the die strength after laser dicing is compared with the die strength after mechanical sawing. Laser dicing is chiefly considered as an alternative to overcome the defects of mechanical sawing such as chipping on the surface and crack on the back side. Laser micromachining is based on the thermal ablation and evaporation mechanism. As a result of laser dicing experiments, debris on the surface of wafer is observed. To eliminate the debris and protect the surface, an experiment is done using a water soluble coating material and ultrasonic. The consequence is that most of debris is removed. But there are some residues around the cutting line. Unlike mechanical sawing, chipping on the surface and crack on the back side is not observed. The cross section of cutting line by laser dicing is rough as compared with that by mechanical sawing. But micro crack can not be seen. Micro crack reduces die strength. To measure this, 3 point bending test is done. The die strength after laser dicing decreases to a half of the die strength after mechanical sawing. This means that die cracking during package assembly can occur.

• Journal of the Semiconductor & Display Technology
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• v.10 no.4
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• pp.131-138
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• 2011

We fabricated distributed feedback InGaAsP/InP laser diodes for optical fiber communication module and characterized the lasing properties in continuous wave operation. The active layer of 7-period InGaAsP(1.127 eV)/InGaAsP(0.954 eV) multi-quantum well structure was grown by the metal-organic chemical vapor deposition. The grating for waveguide was also fabricated by the implementation of the Mach-Zehender holographic method of two laser beams interference of He- Cd laser and the fabricated laser diode has the dimension of the laser length of $400{\mu}m$ and the ridge width of $1.2{\mu}m$. The laser diode shows the threshold current of 3.59 mA, the threshold voltage of 1.059 V. For the room-temperature operation with the current of 13.54 mA and the voltage of 1.12 V, the peak wavelength is about 1309.70 nm and optical power is 13.254 mW.

• Journal of the Semiconductor & Display Technology
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• v.6 no.1 s.18
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• pp.11-15
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• 2007

Low-k wafer engraving process has been investigated by using UV pico-second laser with high repetition rate. Wavelength and repetition rate of laser used in this study are 355 nm and 80 MHz, respectively. Main parameters of low-k wafer engraving processes are laser power, work speed, assist gas flow, and protective coating to eliminate debris. Results show that engraving qualities of low-k layer by using a laser with UV pico-second pulse width and high repetition rate had better kerf edge and higher work speed, compared to one by conventional laser with nano-second pulse width and low repletion rate in the range of kHz. Assist gas and protective coating to eliminate debris gave effects on the quality of engraving edge. Total engraving width and depth are obtained less than $20\;{\mu}m$ and $10\;{\mu}m$ at more than 500 mm/sec work speed, respectively. We believe that engraving method by using UV pico-second laser with high repetition rate is useful one to give high work speed in laser material process.

• Journal of the Semiconductor & Display Technology
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• v.17 no.4
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• pp.37-41
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• 2018

$Y_3A_{l5}O_{12}:Ce^{3+},Pr^{3+}$ single crystal phosphor was prepared by floating zone method. single crystal was confirmed to have a Ia-3d (230) space group of cubic structure and showed regular morphology. The optical properties, single crystal exhibited a emission band from green, yellow wide wavelength and 610nm, 640nm red wavelength vicinity. The luminance maintenance rate was decreased by phonon with increasing temperature, but high luminance is maintained more than powder phosphor. In addition, $Y_3A_{l5}O_{12}:Ce^{3+},Pr^{3+}$ single crystal phosphor was applied to a high power blue laser diode, we implemented high power white laser lightings. and it was confirmed that thermal properties over time, due to the effective heat transfer of complete crystal structure. We confirmed that excellent radiant heat properties than powder phosphor was applied to a high power white laser diode.

• Journal of the Semiconductor & Display Technology
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• v.16 no.4
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• pp.36-40
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• 2017

With an attempt to enhance the visibility of laser beam, we have investigated a black matrix with scattering particles by ray tracing simulations. As the scattering particle density is increased, the detected power by the receiver is increased, thereby enhancing the visibility. In reality, the visibility is reduced with increasing incident angle (away from the normal incidence) of laser beam, a phenomenon also observed by ray tracing simulations. It is due to the fact that the mean path is increased within a highly absorptive BM layer or a smaller number of rays hit the BM area when the incident angle is high. Embedding a number of scattering particles into BM may bring in crosstalk among pixels. However, it is negligible because scattered rays inside highly absorptive BM are re-scattered due to the high scattering particle density, decreasing the power of scattered rays into the active areas.